title: Tyrosinase inhibition by water and ethanol extracts of a far eastern sea cucumber, Stichopus japonicus.
abstract: BACKGROUND
  Tyrosinase plays a key role in hyperpigmentaion and enzymatic browning. The present study was aimed at investigating the inhibitory effects of water and 70% aqueous ethanol extracts of Stichopus japonicus, a sea cucumber long consumed as a tonic food and traditional medicine, on the diphenolase activity of tyrosinase.
  
  
  RESULTS
  In the tyrosinase inhibition study, high-performance liquid chromatography completely separated L-3,4-dihydroxyphenylalanine and dopachrome from other compounds present in the extracts, and provided more reliable results than the commonly used spectrophotometry. The ethanol extract (IC(50)=0.49-0.61 mg mL(-1)) showed higher inhibitory activity than the water extract (IC(50)=1.80-1.99 mg mL(-1)). Enzyme inhibition by the extracts was reversible and of mixed type. For both extracts, the dissociation constants for binding to free enzyme were significantly smaller than those for binding to enzyme-substrate complex. Ethyl-α-D-glucopyranoside (IC(50)=0.19 mg mL(-1)), isolated for the first time from sea cucumber, and adenosine (IC(50)=0.13 mg mL(-1)), were identified as key tyrosinase inhibitors.
  
  
  CONCLUSIONS
  The sea cucumber extracts were demonstrated to possess considerable inhibitory potency against the diphenolase activity of tyrosinase, suggesting that the sea cucumber may be a good source of safe and effective tyrosinase inhibitors.
authors.affiliation: Department of Marine Food Science and Technology, Medical and Bio-Materials Research Center, Gangneung-Wonju National University, Gangneung, Republic of Korea.
authors.forename: Amir
authors.initials: A
authors.lastname: Husni
authors.forename: Je-Seung
authors.initials: JS
authors.lastname: Jeon
authors.forename: Byung-Hun
authors.initials: BH
authors.lastname: Um
authors.forename: Nam Soo
authors.initials: NS
authors.lastname: Han
authors.forename: Donghwa
authors.initials: D
authors.lastname: Chung
mesh_terms: D000241:Adenosine / Q000302:isolation & purification / Q000494:pharmacology*; D000363:Agaricales / Q000201:enzymology; D000818:Animals; D001688:Biological Products / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D002851:Chromatography, High Pressure Liquid; D004295:Dihydroxyphenylalanine / Q000302:isolation & purification; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005960:Glucosides / Q000302:isolation & purification / Q000494:pharmacology*; D045563:Indolequinones / Q000302:isolation & purification; D020128:Inhibitory Concentration 50; D014442:Monophenol Monooxygenase / Q000037:antagonists & inhibitors*; D047528:Stichopus / Q000737:chemistry*
chemical_list: D001688:Biological Products; D004791:Enzyme Inhibitors; D005960:Glucosides; D045563:Indolequinones; C568749:ethyl-alpha-D-glucopyranoside; C001123:dopachrome; D004295:Dihydroxyphenylalanine; D014442:Monophenol Monooxygenase; D000241:Adenosine